1. Field of the Invention
The present invention is directed to a computer tool designed to enhance and replace the physical tape drawing process used in design studios and, more particularly, is directed to tool operation on a large scale display screen, with two handheld input sensors which allows for a smooth modeless transition between creating straight lines and curves.
2. Description of the Related Art
Designers in the automobile industry have traditionally created concept sketches of cars on large scale upright surfaces (walls) that preserve a 1-1 or xe2x80x9cfull-sizexe2x80x9d scale factor between the sketch and the final physical car. The main reason for these full-size upright sketches is that designers and managers want to determine and evaluate the principle curves of a design as early as possible in the design process. Working at 1-1 scale is critical to this, if one wants to avoid the unpleasant xe2x80x9csurprisesxe2x80x9d that might otherwise occur if work were done at a reduced scale or on a conventional CRT, for example. While these measures may seem extreme, it is important to recognize that the product being designed could cost up to $1 billion to bring to market. As such, minimizing mistakes is of utmost importance.
An interesting aspect of these concept sketches is that they are created not by using pencils and paint, but mainly by laying down black drafters tape that feels like common masking tape on the drawing surface.
This style of sketching with drafters tape, called xe2x80x9ctape drawingxe2x80x9d, is achieved by using the everyday skills of unrolling the tape with one hand and sliding the other hand along the tape while fastening it on the surface. Even though the mechanics of this naturally two-handed technique are easily explained, the artwork created by experienced practitioners reflects a level of skill that is on a par with any other artistic medium.
Tape drawing has several fundamental advantages over free-form sketching with a pencil, given the large scale size of the sketches. Firstly, it is difficult to draw, freehand, straight lines and smooth continuous curves at this scale. Physical aids such as rulers and french curves would assist the process, however, they would have to be of similar large scale which unfortunately makes them unwieldy for upright use. Drawing with tape, on the other hand, easily facilitates the generation of perfectly straight lines and, due to the slight elasticity of the tape which allows it to be deformed, smooth continuous curves as well. The freehand nature of the interaction is maintained, and yet the tape""s capabilities help regulate the user""s actions to allow for creation of smooth continuous lines. In addition, tape drawing has the benefit of easily undoing actions and editing compared to drawing with pencils or markers. An undo is achieved simply by lifting the tape off the surface. Editing is performed in two ways: first, by lifting the tape off the surface and relaying it, and second, by tearing off strips of tape and replacing the strips with new tape as required.
While the advantages inherent in drawing with tape have ensured its place in the automotive design process, there are nonetheless several problems with this medium.
Firstly, of all the artists working on the initial design, the skill of the tape artist is the farthest removed from traditional computer graphics systems, and yet, the results of their work must eventually be transferred into the computer. While the resolution and fidelity of the tape from both the input and output perspectives are extremely high, there is no easy way to retain this fidelity when transferring the information to electronic formats. Currently, this transfer process is done laboriously by digitizing the key curves of the tape drawing using a hand-held position sensor and then recreating these curves in a CAD package. This transfer process invariably introduces inaccuracies in the electronic version which then have to be identified and removed. Also, since designers create multiple 2D tape drawings which represent different views (such as a front view and side view) of the under-lying 3D vehicle, these 2D drawings have to be integrated when creating the final 3D model of the vehicle. This integration requires careful alignment and matching of the primary curves of the model, a process that can also introduce errors.
The second major problem with tape drawings is the difficulty in storing and retrieving old drawings. These drawings are typically done on stretched Mylar surfaces which when untacked or removed from the wall contract and distort the drawing. Yet, this must frequently be done to accommodate changes in the engineering drawings that typically underlay the Mylar surface on which the tape drawing is done. Once the drawing is taken down, the purity and accuracy of the original drawing cannot be maintained. Also, the tape itself tends to fall off the Mylar surface after a period of time.
Finally, the physical nature of these drawings preclude easy sharing of design information between different design studios.
What is needed is a digital tape drawing system that will alleviate these disadvantages of physical tape drawing and which would reduce the errors when transferring, retrieving and storing the tape drawings. An electronic system could also provide functionality beyond what is possible using the traditional media.
However, given the aversion of most tape artists to current computer modeling software that require them to learn new skills unrelated to their art, what is needed is a system that will retain the simplicity, fluidity, and capabilities of the physical tape drawing techniques.
It is an object of the present invention to provide a digital tape drawing system that has the capabilities of drawing with physical tape on a large surface.
It is another object of the present invention to provide a system that allows drawing with a bimanual user interface which allows a user to use both hands to draw.
It is a further object of the present invention to provide a system that allows mode switching without an explicit mode switching operation.
It is also an object of the present invention to provide mode switching responsive to proximity or closeness of the input devices to each other in the interface.
It is an object of the present invention to provide a user interface and display system of a large scale suitable for drawing large objects, such as automobiles, at a 1 to 1 scale.
It is also an object of the present invention to provide mode switching that is dependent on which combination of hand(s) are moving at a given time.
It is another object of the present invention to provide a system that allows for drawing of both curves and straight lines without an explicit mode switch.
It is also an object of the present invention to provide a system that allows the smoothness and continuity of curves to be controlled directly and simply by using the input gestures of the user""s two hands.
The above objects can be attained by a system that provides a bimanual user interface in which an input device is provided for each of the users hands. The input devices are used in conjunction with a large format upright display at which the user can stand. The system detects the position of the input devices relative to the display and draws unfastened tape between positions of cursors corresponding to the input devices. By changing the state of the input devices the unfastened tape can be fastened or pinned and unfastened as the user moves one or both input devices relative to each other. During pinning, as the pinning hand moves toward the non-pinning hand, corresponding portions of the unfastened tape are pined. During unfastening a similar correspondence between the reverse movement of the input devices and the unfastened tape occurs. Straight lines are drawn by holding the non-pinning hand fixed while the pinning hand pins the tape. Curves are drawn by moving the non-pinning hand while the pinning hand pins the tape. The switch between straight and curved lines occurs without an explicit mode switch simply by keeping the non-pinning hand fixed or moving it. The radius of the curvature of curved lines corresponds to the separation between the hands as well as the magnitude of simultaneous movement of the two hands. A single input device can also be used to cut the tape and remove it from the display.